Rotary impeller blade



Jan. 14, 1941. y H, E, SANbERS 2,228,611

ROTARY IMPELLER BLADE Filed May l5, 1939 Patented Jan. 14, 1941 UNITED STATES' PATENT OFFICE My invention relates to rotary impeller blades and methods of utilizing the same and while susceptible to many and varied uses, more particu-` larly relates to impellers for aircraft, gas pumps, 5 gas fans, and the like.

With the foregoing in view, an object f my invention is to provide an improved impeller blade.

A further object is to provide such a blade with a normal pitch and a reverse pitch embodied therein.

A further object is to provide such a blade with a normal pitch which grafdually merges into a reverse pitch.

Other objects and advantages reside in the particular structure-of my invention, combination and arrangement of the several parts and in the particular method of operation, all of which will be readily apparent to those skilledr in the art upon reference to the attached drawing in connection with the following detailed description forming a part of this specification.

In the drawing:

Figure 1 is a side elevation .of one form of my 25 invention;

Figure 2 is a horizontal section taken on the line 2 2 of Figure 1;l

Figure 3 is an end elevation of Figure 1;

Figure 4 is a side elevation of a modification;

30 Figure 5 is an end elevation of Figure 4;

Figure 6 is a diagrammatic view similar to Figure 4 showing the method of operation; and

vFigure '7 is a diagrammatic view similar to Figure 6 and showing the method of operation as applied to the form of invention of Figures 1 to 3.

Referring specifically to the drawing, wherein like throughout to refer to like parts, I0 (Figs. 1-3) 40 represents a drive shaft having one end 'connected to any suitable source of power (not shown). The free end of the shaft IIJ has a block I2 fixed thereon for rotation therewith.

A pair of blades II having hubs I 4, each comprising spaced ears, are pivotally connected to the block I2 by bolts or the like I3. Sashaped bands I5 connect the hubs I4 together so that Atheir inclination in use isthe same at all times.

'Ihe structure just described is substantiallyv identical to that disclosed in my co-pending application, Serial No. 229,174, led September 9, 1938. It is to be understood that as far as the balancing of the blades in use is concerned, this form of the invention functions like that em- 55/^/bodied in the aforesaid copending application.

reference characters have been used It will' be noted that the free ends of the blades I I are provided with the normal pitch for directingal current of air rearwardly parallel to the shaft I0 when the blades are rotated in a counter-clockwise direction. However, at least .the rear surfaces I'Ia of the inner portions II of the blades are provided with a reverse pitch. Intermediate the normally pitchedportions I6 and the reversely pitched 'portions I'I are portionsaI Ia which are substantially parallel to the' plane of rotation of each blade and which have substantially no pitch but which merge in both directions into the respective pitches of the portions I6 and II. This structure gives the blades a ,spirally twisted appearance in end elevation (Fig. 3)-. It is to be noted, moreover. that the intermediate portions IIa may be substantially narrower than the portionsl I6 and I'I but diverge gradually in both directions to merge into the widths of these portions. The purpose of the blade structure just described as well as its method of operating will be described later.

Figures 4-6 show a structure similar to that v just describedapplied to an impeller having rigid blades. Here a rotatable shaft is attached bysuitable means 2I to the hub 23 of a two-bladed impeller 22. The outer portions 23 of the blades 22 have a pitch corresponding to that of the portions I6 of therst form of the invention, while at least the rear surfaces 24a of the inner portions 24 have a similar reverse pitch. The intermediate portions `22',a correspond in configuration tothe portions I Ia of therst form.

It is a well known fact that the air in front of an impeller begins to spiral before it is drawn into the blades. It is possibly a not so well known fact that this spiralling body of air is in the form of a vortex, the apex of which is spinning at a much greater speed than are the outer portions. T'he action is like that familiar to everyone in the draining of a wash basin through `the bottom drain. In a rotary impeller, the revverse is true in that thetips of the blades are traveling at a higher rate of'speed than the portions nearer the hub. As in the vortex, the

rotary speed progressively varies from blade tip to hub but in 'a reversed manner as 'the blade speed decreases towards the hub while the vortex speed increases towards the apex.

With respect to thel vortexv created by a rotary impeller blade, I have discovered that there is a definite relation between the spinning speeds of various portions of the vortex with respect to corresponding portions of the blades. That is to say, in the normal impeller-of, say an airning slower than the tipy portions of the blades.

craft-the outer portions of the vortex are spintraveling at the same rate of speed in substantially the same direction so that the blade has little or not effect on that portion of the vortex.

Finally, the apex portions of the vortex are spinning much faster than the corresponding inner Thus, the apex portions portions of the blades.

, of the Vortex tend to drive the inner portions of the blade rather than be driven by them.

However, as the normal blade at this point has the same pitchas tip portion, the spinning apex of the vortex encounters the nonworklng -face of the blade and is deflected forwardly rather than rearwardly and only goes rearwardly when it is drawn into the outer and more swiftly traveling blade portions. `This phenomenon creates a low pressure area back of the blades in the region of the hub, limits the working area of the blades to the outer portions thereof and finally prevents adequate air cooling of the engine driving the impeller which is usually located in that region.

In Figures 6 and 7 I have diagramm-atically illustrated the method of operation of borth forms of my invention. Figure 6 is the form of Figures i and 5 while Figure 7 is the form of Figures 13.

` In these figures, the vortex is diagrammatioally illustrated at V and comprises a slowly spinning outer portion V1 and a rapidly spinning apex V. The outer portion V1 is driven rearwardly by out- -er blade portions 2 3 and I6 just as in the normal impeller. However, the inner vortex portions V2 encounter the rear faces I1 or 24 of the reversely pitched portions 1 and 2l and are deected rearwardly by them, it beingremembered :that the inner vortex .pontions V2. are spinning faster than the blade portions l'l and 24 and overtake them. Thus, the high speed of fthe vortex apex is used to assist the motor while the reverse pitch of the blades at this point directs the vortex 4apex rearwardly along -the shaiits without directing it outwardly as in the usual blade, without causing a low pressure area behind the blades in the axial region. Moreover, cooling of the engine, or motor, by the slip stream is made more efficient and a greater proportion of the blade area is effectively utilized.

the blade speed and the speed of the correspond-- ing portion of the vortex are equal. 'Ihe pitch anjd 'Width of these portions increase in both directions to merge into the pitches and widths of the outer and inner blade portions.. Thus.

where the blade and vortex speeds are equal there is substantially no resistance tothe passage of the vortex through the blade, itfbeing remembered that the vortex as a whole is moving axially of the'impeller--but at the points where there are relative differences between the spinning speeds of the vortex and blades pitched surfaces are provided to utilize this Speed difference.

While in bdth forms of my invention I have shown the front faces of ythe portions l'l and 24 as being reversely pitched as Well as 'the rear faces IIn and 24B, it is obvious that this front pitch is not operative and may be dispensed with if it is found to be detrimental as it may well be at certain speeds.

While I have shown and described what is now thought to be the preferred embodiments of my invention as applied to two-bladed impellers, it is .obvious thlatmy principle can be aswell applied to single bladed impellers, or impellers having more blades *than two. Moreover, it is to be understood that my invention is not necessarily limited to impellers for aircraft but is believed to be equally applicable 'to impellers for gas pumps or fans and possibly to marine propellers an'd fluid pumps and the like. Consequently it is not my intention 'to limi-t myself to the precise structures, uses and methods shown and described except vas hereinafter claimed.

plane substantially parallel to the plane of rotal tion of said blade, and the pitches of said outer and inner blade portions gradually decreasing as they approach said intermediate portion and merging thereinto.

2. A rotary impeller comprising a shaft, at least one blade on said shaft, said blade includouter en'd of said outer portion having a finite pitch, the inner end of said inner por-tion having a reversed finite pitch', said intermediate. portion having a zero pitch, the pitches of said innerand.A

outer portions gradually decreasing as they approach said intermediate portion and merging thereinto.

3. The structure of claim 2, land said intermediate portion being substantially narrower than said inner and outer pontions.

4. The structure of claim 2, and means swingably connecting said blade to said shaft for movement 'about an axis at right angles to said shaft. y HENRY E'. SANDERS.

. ing outer, inner and intermediate portionsgthe 

